Electrode materials for high power lithium-ion batteries has been an area of recent research and development, to meet increasing energy and power demands, e.g. for electric vehicles and storage media for renewable energy. Most of the transition metal oxides that undergo conversion reaction with Li-ions can offer much larger specific capacities over graphitic carbon which can lead to intercalation reaction with Li-ions. Among them, Co3O4 has been given special attention owing to its high theoretical capacity (890 mAh g−1) and good stability. However, mechanical fractures and structural pulverization induced by volume expansion during charge/discharge cycles are major barriers to developing high power lithium-ion batteries with Co3O4 and other metal oxides. To improve cycling performance, various Co3O4 structures, such as nanocage, nanotube, nanofiber, nanowire, micro-flower and nanoplate, and mesoporous morphologies, have been synthesized and tested.
Graphene, a single atomic layer of graphite with large surface area (2600 m2 g−1), with good mechanical property and high electrical conductivity, is an ideal substrate on which metal oxides can be deposited to improve cycling performance and reduce electric resistance. Graphene has also been explored for potential use as anode alone for lithium-ion battery, though it has the disadvantage of irreversible capacity. Typically, it has been applied as a support matrix for other guest active nanostructures. Growth of Co3O4 nanoparticles on graphene and its application as Li-ion battery anode have been reported by many research groups, and it has been noted that its electrochemical properties can be improved by decreasing the oxidation degree of reduced graphite oxide (RGO) when graphite oxide is used as a graphene precursor. For instance, a two-step method has been developed to synthesize homogeneous small metal oxide nanoparticles onto oxidized graphene to improve the electrochemical performance of metal oxide/graphene composites. However, problems persist. As a result, there remains an ongoing concern in the art to provide an anode material to utilize the benefits and advantages available through use of Co3O4 nanoparticles.